Synchronization interface for low power PCS systems

Radio systems using time divided transmissions, either in the form of time division duplexing (TDD) or time division for multiple access (TDMA) must maintain synchronization of the transmission and reception intervals to maximize the system traffic capacity. If there are two or more systems providing coverage for the same area and the transmitting intervals of one system overlap the intervals of another, then severe inter-system interference may occur and the traffic capacity of both systems will be reduced. This paper discusses some simulation results which illustrate the effects of timing errors between systems with common coverage but unsynchronized transmissions. Under some conditions up to half the traffic capability of the assigned spectrum can be lost due to the unsynchronized interference. The paper then outlines a proposed standardized synchronization signal that may be used to synchronize equipment. This signal is generic and may be used to synchronize between systems of the same type or manufacture and also between systems of different origin. The signal is designed to provide an unambiguous timing reference even if the interconnecting wiring is inverted and provides for a timing signal resolution of ±1 μs at intervals of 10 ms and 160 ms. These intervals and resolution are suitable for operation according to the FCC rules for the PCS bands